With respect to installation of speakers and the like in portable information terminals such as conventional cellular phone, ringer for sounding bell sounds, micro motor for producing vibrations or the like has been attached to a cabinet for portable information terminals as a means for receiving call incoming.
Furthermore, it is usual to attach a micro speaker for reproducing received sounds or amplifying recorded messages, and a microphone for collecting voice being fundamental functions in portable information terminal, respectively.
Japanese Laid-Open Patent No. H10-276250 discloses that stereo sounds are listened by users with the use of earphones or headphones in portable information terminals.
In this case, however, there are such disadvantages that unpleasant ache appears at a position where user's ears are in contact with a earphone or a headphone for a long period of time, and that the earphone or headphone must be carried together with the portable information terminal in case of user's movement. Besides, plural persons cannot listen stereo sounds at the same time, so that there has been such a problem that it is insufficient in view of comfortableness and convenience.
Moreover, Japanese Laid-Open Patent No. H8-171477 discloses a workstation and the like for personal computer (PC), and Japanese Laid-Open Patent No. H9-120354 discloses reproduction of stereo sounds by means of a loudspeaker without accompanying an earphone and a headphone with respect to notebook-size personal computer.
In reproduction of stereo sounds through loudspeakers, spatial extensity is required for a sound source, while there is a possibility of appearing cross talk as mentioned hereunder, which is not experienced by the use of earphones or headphones. For this reason, a distance defined between right and left loudspeakers must be maintained at a given distance or more, and an acoustic pressure difference and a phase difference between both ears of an audience must be maintained at a given value or more, respectively, with respect to the right and left loudspeakers.
In this connection, when a distance defined between the right and left loudspeakers is made to be small so that an acoustic pressure difference and a phase difference between ears of the audience decrease respectively, with respect to the right and left loudspeakers, stereo sound effects decrease due to cross talk, resulting in substantially monaural sounds.
In this respect, since a portable information terminal is more compact than the above-described personal computer and the like, a distance between right and left loudspeakers becomes narrower, so that it is difficult to maintain stereo sound effects, whereby there is such a problem that it is difficult to reproduce stereo sounds with high acousticity.
Incidentally, a tendency of multimedia portable information terminal becomes remarkable in recent years, so that mass storage data such as picture image and music must be handled because of increase in a capacity of built-in memory, introduction of a storage medium, and high-speed of communication in portable information terminals.
Moreover, an ownership ratio of portable information terminals including cellular phone is remarkable, and in addition, many persons take along such portable information terminal in case of outing, so that there is a task for elevating convenience to add other extra functions to portable information terminals.
In order to listen high-quality and comfortable sounds derived from multimedia data by means of a portable information terminal, there is such a task that not only stereo sound reproduction of comfortable sounds is required, but also broadband property in frequency of the sounds must be maintained to assure high-quality sounds with respect to portable information terminals.
Furthermore, there is such a task that maintenance of directivity in sounds is required for portable information terminal to listen the same by a plurality of persons in a restricted region, to avoid harassment with respect to surrounding people, and to be suitable for operating environment with respect to portable information terminals.
On the contrary to that described above, there is such a task that omnidirectional characteristics of sounds are to be maintained for listening such sounds by much more persons.
Besides, there is a task of requiring such convenience that two or more persons can catch individually two or more languages or sound sources.
Accordingly, the present invention has been made in view of the above-described problems and tasks. An object of the present invention is to provide a sound reproducing system in portable information terminal, which can reproduce comfortable, high-quality sounds and has high adaptability to operating environment as well as high convenience, and a method therefor.